Today I was moving some cuttings from my Root Riot to cups. I decided to check on some of the ones I have cupped up a week or two ago. I found one that looked like it was failing even though it was starting to show roots against the cup walls. I carefully removed it from the cup, the Root Riot cube was still intact and the roots coming out of it were strong. Starting at the top of the cube, I took a pair of small scissors and cut the cube carefully down one side keeping away from the roots. I was able to fully remove the cube with out breaking any roots. Those roots are tough. After removing the cube to fully expose the cutting I could see that the very bottom half inch was rotting. Using my knife a opened up the bad bark to find larvae under it. I cut off the bad part and most of the root and put it back into it's cup. In the past I had attributed this condition to root rot caused maybe by too much moisture.

That got me to wanting to check out others even though they looked good. Here is a picture of the first one I checked.


Here is another one.
In the cup looking good


Most of the soil removed and showing a little of the rotting end on the cutting.


After cleaning off all of the rotting bark and larvae.


The roots that were attached to the bad bark were still healthy looking, nice and white and tough. It's seems like the larvae weren't attacking the roots but rather the cambium layer right under the bark while leaving the outer layer of bark.

A couple of weeks ago I was doing some reading up on a product that I use to get rid of fire ants and found the part where it talked about others things it kills. One of them is fungus gnats larvae, I know that from trials I've done that it also kills RKN. So when I put the bad cuttings back into cups I mixed some of it in the soil. It is granular so it mixes in easily. Where it isn't recommended for fruit trees and veggies on the label, in other online research I found where it is used in strawberry patches and in citrus groves with special USDA monitoring. Bifenthrin isn't systemic, that is it's not taken up by plants, it stays in the soil. I put one too far gone cutting in a cup with some soil mix and the Talstar granules and capped it tightly. I will check it in a few days to see if the larvae are still alive. Bifenthrin works not as a poison and eaten but by coming into contact with the pest and acting on their nerves in some way. It stays active in the soil for 3 to 6 months, so one application when transplanting should solve the problem until the tree has grown.  I know many of you don't like to use any chemical controls and neither do I, but in the case of fire ants which my wife is highly allergic to, a bite is a trip to the ER, I'm forced to use it. That's how I found out it cleaned out the RKN in had in a certain area of my yard.

Any thoughts or responses are welcome,
"gene"

Here is part of the info.

awful! they have no hearts.

Gene that is incredible . Thanks for posting this.

Gene,
Thanks for posting.
I have had similar a situation, but without the fungus gnats and root riot cubes. After using Rooting Hormone, the cuttings produced lots of healthy roots which grew and filled the 16 OZ cups, then they did not produce any buds. The cuttings eventually dried up. upon removing them from the cups, I had the same conditions of healthy looking roots and dead cuttings. I believe the cause in my case might have been too much moisture and or too high a hormone concentration. Cutting started without hormone at the same time under the same condition are doing fine.

Thank you Gene, you probably saved a lot of cuttings with this post. I just purchased some granules online and I am going to have to pull up a cutting that died after 3 weeks in a gallon pot. This is also thrilling because fire ants are such a problem for us and they LOVE pots!

This happened to me quite a bit this year, two things helped me.  Using the sticky one shot strips hanging above the plants and drenching with spinosad (Monteray Garden Spray) at the same label rate as spraying.  You can use double the rate if you like, it hasn't harmed my plants and usually gives 2-3 weeks protection but I only use it when they get going too much.

Tami,
The Talstar granules have been a Godsend for my wife. Without them she would be house bound. I get mine from our pest control guy, his price is way better than any other outlet. To keep the ants out of the pots just sprinkle some on the ground around the pots, they will not cross it or they die. I use a broadcast spreader and do my whole yard twice a year. I haven't had a nest it years. I do see a stray now and then as they come in on the fence and sidewalks but they never take hold of an area.

I don't know how many trees I've saved but if it is only one or all of mine, to me it's worth it.
"gene"

Interesting find Gene!  Though I am one of those who prefers to avoid unusual or harsh chemical agents, I found it particularly interesting that you say you've seen it kill RKN too.  That is impressive.  I remember seeing someone else on here mention something that got rid of RKN also (not sure, maybe it was the same agent?), but in any case something that'll get rid of rook knot nematodes is definitely worth noting.  Good thread.

Mike   central NY state, zone 5 

Thanks Gene, I may need a RKN weapon in the future.  I did some searching and saw that this material is also available in liquid form.  Wonder why you couldn't drench the soil with a mix of this and say "goodbye to fungus gnats" forever.

Pease follow this link (be careful of your skinand it can cause cancer)

http://npic.orst.edu/factsheets/biftech.pdf

Thanks for the link Vitalucky. I see your concerns but the total outlooks seems very favorable to me. The bad side of bifenthrin is much better than the side effect of most of the medications you see advertised on TV for human consumption and bifenthrin is not made for human consumption. In fact in using it there is very little human contact if used properly. Being that its granular, more like sand, it doesn't adhere to one skin unless it's wet and the fact sheets states that it isn't easily absorbed through the skin of mammals. Breathing it isn't a problem as it is dustless and odorless. No strong chemical smell like most ant poisons. 

If it works on fungus gnat larvae like I think it will, the very small risk which I don't consider a risk, will be worth taking to control or eliminate them. I've been using it successful to control fire ants for years and I haven't started head shaking yet, lol. I appreciate you concerns and bringing them forward. 
Sincere Thanks,
"gene"

A pat in the back goes direct to genecolin for this fungus-gnat larvae-behavior discovery.

It could still be a case of.. which came first the chicken or the egg?  Maybe the rot is there already in these cases and the gnats take advantage, then again maybe not. Some day someone will do a study I'm sure. Thanks for sharing this observation.

I recently purchased a bag of crushed crab shell to mix a bit into my pots and garden to increase calcium and other minerals in my soil(a good source of iodine for us is through plants and what they absorb from the soil). They claim it also helps control RKN(thankfully don't have that problem!). The theory is that crab shells are high in chitin, and that by having a surplus of chitin in the soil it causes colonization of the soil with bacteria that break down chitin. These bacteria then make life difficult for oraganisms high in chitin also, such as RKNs and fungus.
To me the fungus thing is a downfall, because many fungus are highly beneficial to plants root system and a healthy soil web. So I plan on using some, not alot. If I had nematode problems though, I would experiment and use a fair amount in a trial portion of my garden to see if I could thwart the little buggers at the expense of beneficial fungal losses.

Thanks gorgi, but I really don't know what it means. Perhaps sealing the bottom end would help keep them at bay also. I rooted a few today and after soaking in Hormex for 30 seconds I dipped the end into my Bifenthrin granules and the granules stuck to the cuttings bottom end and sides up to 1 inch from the bottom. I then made a planting hole in the mix and put the cuttings in. Now the Bifenthrin is at the most vulnerable place on the cutting. I wet the mix good and put in a spot where the adult gnats can find it easily. we will see in a couple of weeks if it made a difference or not. On a couple I just poured some granules into the planting hole before i put the cutting in. Time will tell.

omotm, perhaps the easiest way would be to use the liquid. I would think that using it once at the original cupping and a little more when first potting up would be sufficient as by the time it loses it power the tree should be well developed. 

I sure hope this works as it is so simple.
"gene"